Universal iOs Applications and Windows based application in Xcode

I am creating a Universal iOs application as part of an assignment (iPad and iPhone :) ). Naturally, they have a UI which I have been accustomed to create through the NIB files, using the fancy drag and drop schemes.开发者_开发知识库 This obviously seems like a great strategy when you are making a dedicated iOS device application.

However, with the universal application, I notice that this strategy can be a challenge since the 2 UIs differ and human error can promote a lack of consistency in the two UI's + double the work!!!

I noticed the solution to the assignment I am doing has the UI created through the AppDelegate file, I have never really done this, and from this stems the questions:

1. What is the appDelegate files for anyways?

2. Is it the way to create the UI for the Universal application through the App delegate? Or do you people still create the UI's through the NIB files meticulously for both iPhone and iPad?

P.S: Side question: This assignment requires me to create a Windows based application vs a View based application which is what I have naturally learnt to do. I understand a Windows based App can grow into a view based application and vice versa. However, I do not understand when you should choose to create a Windows based application?

The AppDelegate in Cocoa is your central Singleton that controls the app workflow. It's used by the underlying Framework to start the application, signal runtime envrionment changes and terminate the app. Being a singleton, it's always there and easy to reference ([UIApplication applicationDelegate]) and it loads up your first view controller.
It's generally common to let the application delegate keep refernces to model and controller objects. But what you describe, the whole UI programmed through the appDelegate, is bad style.
No matter if you use NIB's or you code your UI by manually adding UIElements to the view in code, you should do so in ViewController. Generally, the appDelegate will call the first view controller and that viewcontroller will call all view controller afterwards.